Methods for Calculation of Annual and Extreme Overflow Events from Combined Sewer Systems

Abstract

Overflow from combined systems constitute an increasing source of pollution of receiving waters, as compared to daily wastewater discharges which undergo treatment to a still higher extent. The receiving water problems from overflows are significant both in a long term scale (mean annual load) and in a short term scale (extreme event load). A method for computation of both annual and extreme load is presented. It is based on historical rain series and the use of a time-area model and simple pollutant mixing model in runoff calculation. Statistical calculations for both mean annual load and extreme events have been applied to the computed overflow series. Based on the computerized method simple manual calculations methods have been developed, resulting in graphs and tables for annual load and extreme load.

Modelling, Simulation and Control of Urban Wastewater Systems

“…The treatment efficiency of storage tanks depends on the flow dynamics and on the geometric properties of the tank as well as on their operation. Studies by Johansen (1985) and Durchschlag (1991) give maximum removal rates for suspended solids between 60% and 80%; for particulate COD, Michelbach and Wohrle (1994) estimate a removal efficiency as high as 70%.…”

POLLUTANT LOADS IN URBAN STORMWATER: REVIEW OF METHODS FOR PLANNING‐LEVEL ESTIMATES1

“…Among nonpoint sources, urban runoff was reported as the second most frequent cause of pollution of surface waters, after agriculture (Anonymous, 1986), and the incidence of such impacts is particularly common in urban rivers and lakes. Consequently, urban runoff pollution and its control received much attention during the last 20 years and many procedures for determination of urban runoff pollution loads were reported in the literature (U.S. EPA, 1983;Johansen et al, 1984;Hemain, 1986;Huber, 1986;Harremoes, 1988;Tasker and Driver, 1988;Marsalek and Schroeter, 1989). Recently, this problem was addressed in conjunction with loadings from urban point sources (Marsalek and Ng, 1989).…”